1. Technical Field of the Invention
The present invention generally relates to the mobile telecommunications field and, in particular, to a system and method for automatically reconnecting a disconnected low priority call.
2. Description of Related Art
It is well known that a mobile telecommunications network has a limited number of traffic channels that are used to complete end-to-end connections (air interfaces) between mobile terminal(s) and other users. Because of the limited number of traffic channels available, a mobile service provider, must choose a channel assignment scheme to manage and allocate the limited number of traffic channels. The mobile service provider's choice of a particular channel assignment scheme will, of course, have a direct impact on the performance of the mobile telecommunications network.
Channel assignment schemes can include a service known as "preemption". A preemption service is triggered when all of the traffic channels allocated to a cell are currently busy, and a request is received from within the same cell to use one of the busy traffic channels for a high priority call. Thereafter, the preemption service can forcefully terminate an established connection involving a low priority call in order to establish a connection for the high priority call using the newly seized traffic channel. The conventional preemption service is obviously undesirable to a mobile subscriber given the negative impact resulting from the forceful termination of the low priority call. The mobile service providers often classify calls involving speech or data transmission as having either a low priority or high priority. For example, mobile subscribers may pay a premium to have their calls classified by the provider as high priority.
FIG. 1 shows a time-line illustrating the operation of the conventional preemption service. Assuming all of the traffic channels associated with a cell are busy, then the conventional preemption service can be triggered when an end-to-end connection is in progress for a low priority call between a mobile terminal located in the cell and another user (time period "a"). And, then a channel request for a high priority call is received (timemark "b") causing the preemption service to initiate a first attempt to handover the low priority call to another traffic channel (time period "c"). If the first attempted handover is not successful, then a second attempt to handover the low priority call to another traffic channel may be undertaken by the preemption service (time period "d"). In the event either of the handover attempts are successful, then the low priority call will continue without interruption. However, if both handover attempts fail, then the low priority call will be disconnected (time mark "e") and the high priority call will be connected using the newly seized traffic channel. The duration of the first and second handover attempts (time periods "c" and "d") are determined by the mobile service provider.
Upon disconnection of the low priority call, the mobile subscriber of the disconnected call must actively try to reconnect the disconnected call using another traffic channel (fourth time period "f"). And, if the mobile subscriber is successful in reconnecting the disconnected call, then the call can continue barring another preemption until the mobile subscriber or other user affirmatively terminates the end-to-end connection (time period "g").
In addition to the possibility of having an ongoing call forcefully disconnected without notice, another problem associated with the current preemption service is that the mobile subscriber upon reconnecting a terminated data transmission call must reinitiate from the beginning any data transfer, since the previous call was interrupted. Also, problematic for the mobile service provider is the likelihood that the preempted mobile subscriber will try to re-establish another connection, which further aggravates the already congested situation within the mobile telecommunications network.
Accordingly, there is a need for a system and method to automatically reconnect a low priority call that has been forcefully terminated by a conventional preemption system. There is also a need for a system and method that automatically reconnects a terminated low priority call so that the users will not notice or hardly notice they were disconnected in the first place. Additionally, a system and method is needed that automatically reconnects a disconnected low priority call without interrupting an ongoing data transmission call. These and other needs are satisfied by the system and method of the present invention.